Method of tube drawing with surface temperature control

ABSTRACT

An improved method is disclosed for drawing tubes of larger size and higher quality than obtainable by prior art techniques. The present method is different from those of the prior art at the point of utilizing a technique of closed static blowing in contrast with the open dynamic blowing of the prior art methods. The method of the invention comprises the steps of: A. GENERATING A SUITABLE WORKING TEMPERATURE, B. CONTINUOUSLY DRAWING UNDER SEMI-CLOSED STATIC BLOWING CONDITIONS FOR THE PRODUCTION OF A MIDDLE SIZE TUBE, C. SUBSTANTIALLY CONTINUOUSLY DRAWING UNDER CLOSED STATIC BLOWING CONDITIONS FOR THE PRODUCTION OF A LARGE SIZE PIPE. The present drawing apparatus comprises: A. SPECIAL POT, B. TEMPERATURE CONTROLLER WITH BLOW PIPE, C. STIRRER, D. DRAWING MECHANICS, AND E. CUTTER AND GRASPERS.

United States Patent [191 Minegishi [451 Apr. 9, 1974 METHOD OF TUBE DRAWING WITH SURFACE TEMPERATURE CONTROL [76] Inventor: Susumu Minegishi, 729

Higashiterao-cho, Yokohama, Japan [22] Filed: July 25, 1972 [21] Appl. No.: 275,035

Primary E.\'aminerFrank W. Miga Attorney, Agent, or FirmFidelman, Wolffe, Leitner & Hiney [5 7 ABSTRACT An improved method is disclosed for drawing tubes of larger size and higher quality than obtainable by prior art techniques; The present method is different from those of the prior art at the point of utilizing a technique of closed static blowing in contrast with the open dynamic blowing of the prior art methods. The method of the invention comprises the steps of:

a. generating a suitable working temperature,

b. continuously drawing under semi-closed static blowing conditions for the production of a middle size tube,

c. substantially continuously drawing under closed static blowing conditions for the production of a large size pipe.

The present drawing apparatus comprises:

a. special pot,

b. temperature controller with blow pipe,

c. stirrer,

c1. drawing mechanics, and

e. cutter and graspers.

1 Claim, 21 Drawing Figures PATENTEBAPR 9 I974 SHEEI 2 0F 7 FIG. 2-c

FATENTEU APR 9 I974 SHEET 5 BF 7 'vQI METHOD OF TUBE DRAWING WITH SURFACE TEMPERATURE CONTROL According to the present invention, in addition to tubing in general, a small scale plate glass and ceramic tubing are similarly obtainable.

The present invention relates to a method and apparatus for drawing glass tubes or cane, especially in larger diameters and higher quality than those that can be obtained by the prior art procedures or conventional techniques.

The term glass" as used in the present disclosure means all those materials having similar softening and viscous melting characteristics of general glasses.

BACKGROUND OF THE INVENTION There are both horizontal and vertical drawing methods in the field of glass tube manufacture. In the former processes, examples are Danners and Vellos methods, and the like. And the latter processes include Schullers method (as diagrammatically shown in FIG. l-a), Corning's method (as diagrammatically shown in FIG. H2), and Lubbers method (as diagramatically shown in FIG. I-f). FIGS. l-c, l-d, and I-e show a schematic description of the principles of tube and sheet glass making.

Among the reference numerals therein shown, 1 is a tube forming cone, 2 is the die of Fourcaults process, 3 is the draw bar of the Penvernon process, 4 is a glass tube, 5 is sheet glass, 6 is a sleeve, 7 is a cooling means, 8 is molten glass, 9 is pressurized air, and 10 is a bait.

Lubbers method, shown in FIG. l-f, is a large glass pipe, say 1.2 meters in diameter, drawing method that was worked from about the 18th century until the beginning of the 19th century in various countries for the production of window glass.

The present invention is a method applying the principle of Lubbers technique. All vertical drawing methods can be classified into two types depending upon the type of air blowing:

(I) Open, dynamic, type and (II) closed, static type.

Only Lubbers method is the closed type in the prior art. The aforesaid horizontal and all other vertical methods are of the open type. The open blow drawing method is suitable for relatively small tube making and mass production, but in spite of the high dynamic pressures available, an inner static pressure cannot be created. Therefore, the tube diameter cannot be increased.

For example, by Schullers method (shown in FIG. l-a) the maximum diameter amounts to only 30 millimeters diameter, and by Danners or Vellos methods, it amounts to 40 m.m. diameter. Cornings method can produce up to 180 m.m. diameter tube by using a big forming cone 1 as shown in FIG. l-b, and by its expanding action on the trumpet-shaped base of soft glass. Nevertheless, the maximum diameter cannot be increased above 180 m.m. diameter.

On the contrary, the closed method of this invention can expand the tube diameter as large as the size of the later-mentioned drawing pot (as shown in FIGS. 2 and 2-c). The diameter of the latest Lubbers pipe amounted to 1.2 meters in diameter, and the more enlarged size of the later-mentioned pot enables production of still larger diameter glass pipe by the present invention.

On the point of quality, because the aforesaid forming cone 1, which is a frusto-conical refractory sleeve, is abraded against high temperature viscous soft glass, and as the frustum edge of the cone as shown at I (in FIGS. l-b, l-a) is worn, defects of cords, strial, and blisters are successively created in the case of Schullers and Cornings process.

On the other hand, the present invention uses no such cone, with the result that no such defects occur. These defective phenomena resemble the case of sheet glass making where the slit edge of the die of Fourcaults process cause cords (as shown in FIG. l-d), but the Penvernon process (as shown in FIG. l-e) has no such refractory near the glass level and no such cords are created. The origin of forming such defects is diagramatically illustrated in FIGS. l-b and l-e, which compare the effect of a cone or no cone. Moreover, the replacement operation of the worn-out cone 1 causes idle time and working loss.

To avoid these defects and working loss, British Pat. No. 1,057,944 and German Pat. No. 892,366 disclose the method of applying platinum foil on the edges of the cone. Despite the advantages of a larger pipe and betterquality, the reason Lubbers method has not been used is the discontinuity of production and a fluctuation of diameter. Lubbers process has been generally considered not industrially economical.

DESCRIPTION OF THE DRAWINGS The particular features of the method of the present invention can be readily understood by reference to the drawings wherein:

FIG. 1 (ainclusive) is illustrative of the prior art as hereinabove described;

FIG. 2 shows an apparatus of the present invention, in part, particularly adapted for drawing small tubing;

FIG. 2(a) is a plan view of the draw-bar or floater employed in the apparatus of FIG. 2;

FIG. 2(b) is a sectional side view of the draw-bar or floater of FIG. 2 illustrating means for maintaining pressure in the drawn pipe and temperature 'at the drawing surface;

FIG. 2(0) is a plan view of the drawing pot employed in the apparatus of FIG. 2;

FIG. 3 is a sectional elevation of the apparatus of FIG. 2 with associated elements for drawing and cutting large diameter tubing;

FIG. 3(a) shows an elevation and a plan view of the blow head of the apparatus of FIG. 3;

FIG. 3(b) shows an elevation and a plan view of an alternative blow head construction;

FIG. 4 is a detailed view of the drawing and blow head elements of FIG. 3;

FIG. 4(a) shows a detailed view of one embodiment of means to insert or withdraw the blowhead;

FIG. 4(b) is a sectional plan view at AA of FIG. 4;

FIG. 5 is a detailed view of the tubing cutting means of FIG. 3;

FIG. 5(a) is a plan view of the cutter means of FIG. 5;

FIG. 5(b) is a detailed view of one embodiment of means for actuating the cutter of FIG. 5;

FIG. 5(0) is a detailed view of alignment means associated with the cutter actuator of FIG. 5(h); and

DETAILED DESCRIPTION OF THE INVENTION To overcome these disadvantages, the present invention adopts a later-mentioned mechanical arrangement for the elimination of discontinuity, and a static substantially shockless drawing method with an automatic control system for control of diameter fluctuation. By this method, satisfactory results have been obtained. These techniques are similar to the present sheet glass system.

In FIG. 1, there are compared tubing processes with sheet glass on the occurrence and origin of cords and striae.

Cornings process as shown in FIG. l-b blows out jet air from a newly cut opening after the tube has been broken off. The high dynamic blow pressure then falls suddenly. Simultaneously a shock wave is transmitted to the soft trumpet-shaped base glass. Thereafter, the shock causes a tube diameter fluctuation which declines as a damped oscillation and that fluctuation causes dimensional inaccuracy defects.

Because of this tube diameter disturbance at its cutting, the open tubing shows dimensional variations. On the contrary, the closed, static pressure blowing, by Pascals isobaric theory, acts isobarically on the interior of the tube so that the tube is formed exactly round and of uniform wall thickness. Because of low static pressure, say 10-60 millimeters water gauge, no shock or very little is caused by cutting. Therefore no, or little, diameter disturbance is created. Such tubing is superior to the products of open, dynamic processing, such as by Cornings method.

Moreover, when one piece of tube is ended, the grasper means 24 of the middle stair (as shown in FIG. 3) grips the tube, whereupon the head 27 is put into the newly cut end of the tube and pauses until the inner pressure of the tube is raised to the prior inner static pressure so that no (or slight) diameter fluctuation is created. If only a slight cylindrical fluctuation is created, the width of its ring is very narrow.

In a strict sense of the word, the operation is discontinuous but because the width of the diameter of the disturbed ring portion is very small at most, the method is superior to all open dynamic blowing systems.

Next, if the tube cutting is difficult, it can be heated by contacting with an electrically heated element, for example Ni-Cr, wire, or a sharp burner as illustrated in FIG. 5, and thereafter quenched on the heated scratch line by a cold water drop and then broken off.

The necessary conditions of a kiln for tube drawing is to regulate the glass temperature to working temperature. For this purpose the present invention uses a relatively short forehearth and continuously supplies molten glass therefrom to a modified, inverted. frustroconical shaped pot, as shown in FIGS. 2 and 2-c. A blending stirrer 11 is installed therein which, by its pushingaction, transmits the molten glass to floater 3 at a suitable temperature to provide an isothermal working zone.

An annular refractory body, herein called a floater, whose construction is explained in detail in FIGS. 2-a and 2-b, is located below the glass surface and cools the neighboring molten glass to a suitable temperature for drawing. The automatic rise and fall of the floater 3 enables control of the temperature of the upper layer glass in the pot. The automatic temperature control system is necessary to maintain a proper working range and provides good drawing conditions.

FIGS. 2-a and 2-b show the construction of the floater 3. There are water cooling inlet pipe 15, outlet pipe 16, which cools the neighboring glass layer by conduction through insulator 18. Between and adjacent to the two cooling pipes, blowing air pipe 17 extends into the center of the floater 3 where the blow nozzle 21 of air pipe 17 opens upward. The water cooling pipes 15,16 operate to preserve a constant working temperature and constant position and prevents the blow pipe 17 from wearing by heat. As shown in FIGS. 2-a and Z-b, the ring-shaped water pipe and straight water pipe 20 provide a flow of cold water and the air pipe 17 is protected by the cooling effects.

The air nozzle 21 in FIG. 2-b is made of heat-resistant metals or ceramics andis changeable when worn or when a length change, corresponding to the variation of the depth of molten glass, is necessary.

The refractories 18,19 in FIGS. 2-a and 2-b, which are shown by thin dotted lines to explain and clarify the location and operation of the water cooling pipes, are made of porous, heat-shock resistant refractories and are fitted above and below iron pipes 15,16,17.

The functions of the refractories 14,19 are to prevent over-cooling of the neighboring regions of the glass or over-heating from the hot glass stream from forehearth 13. Floater 3 corresponds to drawbar 3 of the Penvernon process in FIG. l-e because there is no cone near the melt surface.

FIG. 2 illustrates a continuous drawing process of small size, for example, 2-40 m.m., diameter glass tube. Therein, as shown respectively, 11 is a stirrer, 12 is the aforesaid modified inverted conical frustrum shaped pot, 13 is the forehearth; hot molten glass stream flows therefrom into said pot 12 an overflow passes from over hole 12'.

The molten glass stream is mixed and pushed forward by stirrer l1 and it flows down along the inside slope of the pot and the stream flow is directed onto floater 3. By the moderate cooling of floater 3, the molten glassy layer in the neighborhood attains a suitable temperaturefor drawing glass tubes and by injection of blow air from the nozzle 21 and the operation of drawing roller or catapiller 22, glass tube is continuously drawn.

The suitable temperature to draw the glass tube is adjusted by (1) the rise and fall of floater 3, and (2) an inclination angle to horizontal and rate of stirrer 11.

As the inside slope of aforesaid pot effects the direction of the glass stream, a simple evaluation of the slope should be conducted to determine the relationship between an inclination angle and revolutions per minutes of stirrer 11 to obtain correct dimension, roundness, thickness of tubes.

FIG. 3 illustrates the manufacture of large diameter glass pipe, say over m.m. diameter. The reference numerals up to 22 are the same as in FIG. 2, and 24 on the middle level shows an assembly of grasping equipment, 25 shows a pipe cutting assembly, and 26,27,28,29 on the upper level show the drawing superstructure which is illustrated in detail in FIG. 4.

The gear of the drive 29 (1) in FIG. 3 engages with rack 49 which is constructed at a position where there is no hindrance to motion. The power elements 29 are comprised of an eddy current coupling motor 29, gear reducer with brake 45, reverse and quick returning apparatus (later mentioned) on the girder 26. In some circumstances, particularly in the drawing of large size pipes, the power elements (motor and reducer, brake, etc.) become so heavy that it is difficult to balance and to operate. As an alternative, there is illustrated series 30 apparatus comprising the aforesaid motor, reducer with brake, quick return device, and the like, and a rope drum 30 set on a platform which is constructed half way up the superstructure outside of the guide pole 46 and raises the girder 26 by a rope or chain drivve.

For small diameter tubes, it is suitable to employ the process of FIG. 2.

The operation of the apparatus of FIG. 3 is as follows:

A tool for beginning the draw of a glass tube is the socalled bait as shown at in FIG. l-f. Using manual controls, after trial drawing and the correct diameter pipe is properly leveled out, continuous drawing starts. First, the cutting apparatus 25 adheres to the tube and is drawn up with it by operation of solenoid 51 as shown in detail in FIG. 5. The cutter begins to scratch while simultaneously grasper 24 grips.

Thick walled pipe often cannot in one step be cut by cutter 50, so then electrically heated element 56 heats on the scratched line 50, which is thereafter quenched by water and cut down as illustrated in FIG. 5. Of course, the cutting process can be accomplished by hand, including scratching by the wheel cutter and heating by electric heat element winding. But hereafter the preferred automatic process is described.

Next, the cutter 25 retracts and waits until the next cycle begins.

Meantime, the grasper 24 tightly grips the pipe from just below the cutting level of 25, and the superstructure 26,27, etc. is put into newly cut pipe hole 4 and the grasper 24 is released until a subsequent cycle.

The blow head 27 in FIG. 3, which has drawn a length of glass pipe, is extracted from out pipe 4 and the cut pipe is cleared away. The superstructures 26,27, etc., quickly goes down to newly cut pipe opening 4 and is inserted. Thereafter, the air 35 begins to blow into the new pipe opening which is immediately drawn up. Alternatively, if the blow nozzle located at the center of the aforesaid floater 3 in said pot is employed, the heads 27 should be a closed cap. The grapser 28 and inside grasper 41 in FIG. 4 grip the pipe end 4 which begins constant speed drawing by the power line 29 or 30 in FIG. 3.

The lower section of pipe 4 just after cutting pauses in place until its inner static pressure is attained.

Immediately after the blow head 27 is put into the new pipe opening, air blowing 35 is started and the inner static air pressure raised to an adequate level, say l0-40 m.m. W.G. The air volume blown into the tube is relatively small, and it is raised instantly to suitable and necessary inflating pressure.

For example, when drawing the 120 m.m. diamete n pipe, the inner pressure should be 10-40 m.m. W.G.'

attained in about 1 second, and at a drawing speed of 0.9 m/min., the fluctuated width of the cylindrical ring becomes 0.8 cm.

If the draw after a stop is not begun before the inner static pressure, said lO-40 m.m. W.G. is attained, no diameter fluctuation occurs at all.

Next, the loosely sealed blow head 27 with constant gap 23, 23', 23" is employed as follows. A big pipe drawing process is illustrated as in FIG. 3. It is necessary (I) to raise the inner static pressure, and (II) to grip the pipe without slippage. Middle size tubes as 40-80 m.m. diameter are capable of continuous drawing by a mixed method of FIG. 2-FIG. 3 as follows:

As shown in FIG. 3-a, characterized by (I) holeless blow head 23 with constant gap 23" between 23 and tube inside 4, (or as shown in FIG. 3-b) a blow head 23 with constant gap fold 23 and (II) continuous draw roller or catapiller located below grasper 24 and cutter 25 in FIG. 3, air blown from the nozzle 21 and the gap causes a resistance to flow and the residual air therein creates the constant static pressure.

For an example, it is sufficient to draw up 60 m.m. diameter tube with 200 m.m. W.G. blown air from nozzle 21.

To draw up glass tubing, it is necessary that it be tightly gripped by rollers or catapillers and, the more tightly, the less slippage that occurs.

The operating process of the loosely sealed head 23 in FIG. 3-a and 23' in FIG. 3-b is firstly by power installation 29,45. The head 23 is drawn up at constant speed with pipe 4 and in the next stage of the process, reversed and quick returned. It is absolutely necessary that the tube draw speed by the rollers coincides with the head 23,23 by regulating the drawn speed of the power 39 elements. The best method is as shown in FIG. 3-1;, that (I) afew notches are cut around the head 23 or 27, or (II) a narrow band of heat resistant rubbers or asbestos is stuck around the outside surface of the head 23 or 27 itself. Thus the gaps 23" are made and through these gaps the air is blown out. Thus the notched or narrow banded head 23' is put into the end opening of the cut pipe grasped by 28, stuck into pipe 4. After cutting by 25, the head 23 elements quickly go down to the newly cut portion pipe and so on repeatedly in almost the same action in FIG. 3.

The constancy of the static pressure of the interior of the glass pipe is necessary so the blown air therein should be automatically controlled and exactly ordered by a timer. The details of every unit apparatus and its operation are as follows:

I. Glass pipe drawing head in FIG. 4.

This apparatus comprises mainly drawing head 27 and pipe grasping system, constant speed drawing and returning mechanics, and blown air or closing apparatus.

In FIG. 4, the inside body of the frustro-conical shaped head 27 is composed of a heat resistant rubber and its outside layer by an asbestos and rubber mixture. 28 is the same apparatus as 24 in FIG. 3, which grasps tightly the outside of glass pipe 4. Under part of the girder 26, 29 is a motor with reducer and brake which raises and lowers these drawing head elements. Alternatively, 30 is the same assembly employing roping drum, etc., on a separate mount.

The separately mounted series does not load its driving power on the girder 26, but on the fixed stage of the middle level construction. The return system that provides constant speed rise and quick return is well known in both electrical and mechanical operations and the lowest end should be provided with a shock absorber (not shown). 32 is a rack, 33 is a metal guide for blow pipe 34 which FIG. 3 shows in section for clarity. 31 is a pinion.

Blow pipe 34 is welded to the back side of 32 and blown air 35 is passed into it. The lower side of head block 27 is hollow and an iron disc 37 fixed with thin bolt 36 and an air seal curtain 38, which is made of a soft leather or rubber, is placed between the hollow side of head 27 and the bolt top 36 and softly tightened.

FIG. 4-b shows the section AA of FIG. 4 and illustrates the disc 37 and bars 39 whose tip hole holds an end of bell crank type lever 40. The soft leather curtain 38 is pushed to inside of glass pipe 4 by piece 41. Above the disc 37 in FIG. 4, the spring 42 is put between it and the rectangular flange of bars 39. Solenoids 43 act upon the flange. 44 is a supporter of the lever 40 which is the fixed lower part of blow pipe 34.

45 is a motor and reducer with a brake and the drive 45 inserts and withdraws the head 27 and the brake prevents automatically over-pushing of the head 27 and simultaneously spring 42 pushes the pieces 41 against the inside wall. Simultaneously the fastener 28 grasps the outside of pipe 4 so that the pipe 4 is tightly gripped.

In the large size pipe drawing, this driving assembly 45 becomes too heavy and difficult to balance. A solenoid system suitable for insertion and withdrawal of the head 27 is shown in'FIG. 4-a, diagramatically applying the principle of grasper 24 in FIG. 6. The reference numbers of its right side are the same in FIG. 6 and that of the left side are the same as in FIG. 4, wherein 31 is a projected pin inserted in the hole of lever 71 and 70 is a fixed shaft. If the solenoid 73 acts in the arrow direction, and in order 75-70-69-68-70-71-31'--- -operate, the head 27 is pulled out from pipe 4 and when the action of solenoid 73 is released by the reverse operation of the spring 74, the head 27 is put into the pipe end 4.

The operation of FIG. 4 apparatus is as follows. The girder 26 which supports the head 27 and power 29 etc. in FIG. 3 quickly falls to the newly cut end pipe 4 and by simultaneous action of elements 45-31-32-34 as aforesaid, the head 27 is pushed into pipe 4 and automatically stopped by the brake which should be actuated electrically or mechanically for exact regulation. The lever 40 and the pieces 41, and also the air seal 38, are pushed to the inside wall of pipe 4 by the springs 42, where they prevent the air leakage and keep constant static pressure. The blow head 27 is indirectly fixed to the girder 26. As soon as it begins to blow air 35, the draw of new glass pipe at constant speed by the apparatus of FIG. 4 is begun. The rollers 47 and connecting spring 48 must be smoothly pushed on the guide pole 46 to prevent fluctuation of the pipe diameter at the draw. For middle size tube manufacture, i.e., about 40-80 diameter, the inside tightening and air sealing action 38,39, 40,41 series can be omitted and only outside fastener 28 is necessary, but for tubing more than 80 mm. diameter, both inside and outside grasping are necessary.

After the glass pipe is formed with no diameter fluctuation, and a definite length of pipe is drawn, the rise of girder 26 is stopped, the action of solenoids 43, push spring 42,39, levers 40, and pieces 41, and curtain 38 leave from inside pipe 4. Then the elements 45,3l,32,34 series operate and pull out the head 27 from the end of pipe 4 and cut pipe 4 is removed by hand. These operations are thereafter repeated cyclically.

Next a glass pipe cutting apparatus is illustrated in FIG. 5'. Reference number 50 is a wheel cutter (its material is, for example, tungalloy, ceramics, etc.,). 51 is a solenoid which draws spring 52. 53 is a low speed power means with low speed reducer. 54 and 55 are combination bevel gears or spur gear and pinion which act to rotate the cutter 50 aroundthe glass pipe 4 by the action of element 53 and scratch the outside surface of pipe 4.

56 is an electrically heated element, 57 is an insulator holding the element and 58 is a solenoid. Elements 56,57,58 tighten the element 56 by brake action. 59 is a bell crank lever situated in the hollow part of the base 85'. 60 is a projection on the shaft of cutter 50. 61,61 are projections of 59 and 62 is the girder loading all the cutting apparatus on rollers as in the case of 47 in FIG. 4. 63 is a pinion and 64 is a rack. 65 is a base ring welded to 62.

As shown in FIGS. 5 and S-a, between the aforesaid reducer and bevel gear 54 a conventional arrangement 82, which acts as a start and stop timer, connects to said 54 and 55. By the revolution of 54 and 55, said cutter 50 scratches the line 50'. The opposite side of 82, a conventional mechanical arrangement 83 which acts as regular run, speed change, reversing, and stopping control, connects to pinion 63 engaged with rack 64 which is constructed with no hindrance to the motion.

By the rotation, reverse motion and stopping of 63, aforesaid girder 62 rises, reverses or stops in any position. The connection of 83 to pinion 63 is by any arrangement desired so the position of 6 3 and 64 are shown by thin dotted lines.

FIG. S-a shows the plan view of FIG. 5 and illustrates especially the operation of electric heating element 56 by the action of solenoid 58, operating lever 79,78 and 57 in FIG. S-a, which wind and tighten 56 around the pipe 4 and by applying current cause the red heating of 56. By water quenching on scratched line 50', the cut is completed.

The bevel gear 55 joins with base disc 85 by circumferential contact which comprises a round hole for glassy pipe 4 and lateral hole 85', which includes the place for operating the electric heat element 56. 55 and 85 prevent vibration by the vertical roller 84 situated between them. 81 is the position fixing end of the element 56 on the base disc 85.

FIG. S-b shows the fallen element 56' which, by the anti-arrow direction of solenoid 58, loosened and fell onto the insulator 61. After the pipe 4 is formed and is ready for red heating on scratched line 50', the device elevates the element 56' on 61' to the line 50', by the orderly action of 60,61,59,61 as aforesaid. 87 is a spring which pushes 61 up.

FIG. 5-c shows the device for elevating the element 56' to the line 50' by solenoid 86.

The operation of the cutting apparatus is as follows:

Just before the girder 26 in FIG. 3 ends the forming operation of glass pipe 4, solenoid 51 acts, the cutter 50 quickly contacts glass pipe 4 and by continuous revolution of series 53,82,54,55, the cutter 50 scratches a line 50' on pipe 4. Thenafter the solenoid 51 stops the cutter 50 pulls back.

A soft glass or thin-walled pipe can cut by such process alone, but hard glass or thick-walled pipe is diffcult to cut. In the latter case, when the small projection 3 802 8 5 8 9 H 10 with rollers 60 which is stuck to the rod 88 pulls itself 69, 68,71,66,67 act, grip, tighten and hold the pipe back, it pushes 61 which is the end of lever 59 and without distortion. When the upper drawing apparatus pushes up the electric heating element 56' laid upon 26 retracts quickly to the opening of newly cut pipe 4, the insulator 61' to line 50'. The end of said element he gripping apparatu in FIG. 6, by action of the sole- 56 is fixed on the insulator 61' located on the base disc 5 noid 73 pp to the arrow direction,

85 in FIG. 5a and another end is fix d t lever 79, th series are loosened and withdrawn from pipe 4 and do end of which is connected to solen id 58 as sh wn in not contact pipe 4 or interfere with the next constant FIGS. 5 and 5-a. By the pulling action of the solenoid p e drawing of element 6,27,29-

58in the arrow direction, orderly operation of 79, fixed Reference number 28 in FIG. 3 is the same device of pin 78, and insulator 57,56 causes element 56 to wind 10 24 and acts timely to grasp or releasepipe 4. round the periphery of glass pipe 4 and an electric For the necessity of putting 68,69,68',69 of FIG. 6 charge is supplied on it. into the hollow 80 of part 55 in FIG. 5, arms 72,72 and The red-heated element 56 heats on scratched line 75,75 construct a two-step system as shown at 24 in 50. During the heating 56, the pinion 63 operates with FIG. 3. And these two steps of grasper 24 are installed rack 64 at suitable speed to elevate 62 with 56 which beneath girder 62, partially within the ring base 65 in is sticking to drawing up glass tube 4. After a short time FIG. 5, as in the case of 28 and under part of girder 26 of the heating, the current is stopped and the element in FIG. 3. The operations of FIG. 2 and FIG. 3 appara- 56 is loosened by reaction of solenoid 58. Water is aptus are controlled by a timer. And all glass tube diameplied on line 50' and the pipe is cracked off. Then, by ters, blown air pressure, and temperatures of the inner reverse movement of 83 and gear 63 series, the cutting layer Of the Pot are aut -Co tro led.

apparatus retracts to its initial position. The apparatus of FIGS. 4, 5 and 6 shown one exam- The necessity of preventing the obstruction of inserple but should not be construed as limiting.

Example I Stirrer Tube Fluctuation Working Inclioutside thickof outside Samp. temp. rpm nation dia. ness diameter Sodalime glass 1.000C. 2l 73 75 mm. 4.5 mm. $0.6 m.m. Lead glass 940 is 73 64 4.0 0.2-0.4 Borosilicate I glass (1 1,090 23 73 20 1.0 0.1-0.2 Borosilicate glass tion of the blow head 27 into the nviil 'eiit'hii Sfiifii Glassy material comprising, beside s"gnersi giiissa, 4 requires that all cutting apparatus, including gripper ceramic. materials, earthen and mineral ores, molten 24 in FIG. 3, be retracted by pinion 63 and girder 62 products of high polymers and having similar softening to a fixed po'sition,-stop and remain until the next cycle. and melting characteristics of general glasses can be employed, as exemplified by the following procedure: FIG. 6 is a glass pipe gripping apparatus, in principle 1 applied to 24,28 in FIG. 3, 58,79,78,57 series in FIG.

5. Reference numbers 67,67 in FIG. 6 are formed by EXAMPLE 11 heat resistant rubber or asbestos on a narrow iron band 66. 68 and 69 are the sector gears inserting the shaft 70 To c o y Obtained in p there a d ed which is fixed to the base. 71,72 are connecting levers, 10-15 percent Dolomite by weight. The softening tem- 73,73 are solenoids and 74, 74' are fixed springs. perature of the mixture is I,050-l,200C. and it is The operation is as follows: melted to a flowable state at l,380-1430C. and the When the girder 26 and the head 27 series in FIG. 3 ceramic composition obtained is assayed as follows:

s10 lino, 15,0, 6.6 M 0 615,0 'ico "'rio,""""'roiai 61.3 16.2 7.01 10.03 3.19 1.80 0.8 0.1 99.33

have ended the pipe forming and reachedthe topposi T Using the aforesaid shaped psi'ind temperature contion and stopped just before starting the cutting action troller, a light black transparent tube consisting of the of 25, by the action of solenoid 73, in the arrowforegoing composition wasformed, containing almost direction, elements 75,69,7ZPUSI1 to glass pipe no alkali and highly resistant to chemical corrosion:

4 and simultaneously, by engaging sector gears 68 and What is claimed is:

1 1' l. The method of drawing cylindrical glass tubing from a molten or plastic mass comprising the steps of:

a. forming a horizontal, planar drawing surface of said molten or plastic mass; 5 b. causing said molten or plastic mass to continuously flow vertically through a temperature control zone immediately adjacent to and submerged beneath said drawing surface; c. adjusting the temperature of said molten or plastic mass in said temperature control zone to a drawing temperature;

d. vertically drawing at a constant rate a cylindrical tube from said drawing surface;

e. applying a constant relative fluid pressure from ten to sixty millibars above ambient pressure to the interior of said cylindrical tube;

f. withdrawing heat from said cylindrical tube; and

g. continuously replenishing said molten or plastic mass. 

